What is the name given to the process where particles settle down on the floor of a chamber?

In the reaction $SO_{2(g)} + 2H_2S_{(g)} \rightarrow 3S_{(sol)} + 2H_2O_{(l)}$,which method is used to obtain the sulfur sol?

$Fe(OH)_3$ is a positively charged sol. For its precipitation,the best precipitating agent is:

For coagulating $As_2S_3$ colloidal sol,which of the following will have the lowest coagulation value?

Tyndall effect is observed only when:
$(i)$ the diameter of the dispersed particles is not much smaller than the wavelength of the light used.
$(ii)$ the refractive indices of the dispersed phase and the dispersion medium differ greatly in magnitude.
$(iii)$ the size of the particles is generally between $10^{-11} \ m$ and $10^{-9} \ m$ in diameter.
$(iv)$ the dispersed phase and the dispersion medium can be seen separately in the system.

Which of the following statements is not true for a lyophobic sol?